1. Field of the Invention
The present invention relates to a display device, and more particularly, to a liquid crystal display device having a reduced profile and a method of fabricating the same.
2. Description of the Related Art
In general, a liquid crystal display (LCD) device includes a first substrate, a second substrate, a liquid crystal material disposed between the first substrate and the second substrate, wherein one of the first and second substrates is a thin film transistor substrate (TFT substrate) and the other is a color filter substrate. In addition, the LCD device includes a backlight assembly disposed at a lower portion of an LCD panel to irradiate light.
The TFT substrate commonly includes gate bus lines and data bus lines that are formed on an inner surface of the transparent substrate in a matrix configuration. Thin film transistors (TFTs) function as switching devices and are formed at intersections between the gate bus lines and the data bus lines, and pixel electrodes are formed in unit pixel region contacting with drain electrodes of the TFTs.
The color filter substrate commonly includes a transparent substrate, a black matrix (BM) formed on an inner surface of the transparent substrate, a color filter layer, and a common electrode. The liquid crystal material is interposed between the color filter substrate and the TFT substrate.
During operation of the LCD device, a driving circuit supplies a voltage to the gate bus lines and the data bus lines. As the voltage is supplied to the gate bus lines, the TFTs disposed at the intersections between the gate lines and the data lines to which the voltage is supplied, are turned ON or OFF. Then, charges are accumulated in the pixel electrodes connected with the drains of the turned-ON TFTs and a voltage supplied to the common electrode induce an electric field to the liquid crystal material. Accordingly, orientation of liquid crystal molecules of the liquid crystal material are changed in each unit pixel region. Thus, transmission characteristics of the liquid crystal material are changed such that light is permitted or prevented from traversing through the liquid crystal material and color filter, thereby producing a colored image.
FIG. 1 is a cross sectional view of a TFT substrate according to the related art. In FIG. 1, a gate electrode 102 is formed on a transparent substrate 101, and a gate insulating film 103 is grown on the gate electrode 102 by a plasma enhanced chemical vapor deposition (PECVD). Next, an amorphous silicon layer and an phosphorous-doped amorphous silicon layer are sequentially deposited and patterned using photolithographic processes to form a channel layer 104 that includes an active layer 104a and an ohmic contact layer 104b. 
Next, a metal layer is deposited on the substrate including the channel layer 104, and is patterned by photolithographic processes to form source/drain electrodes 105 and 110 that contact the ohmic contact layer 104b. Then, a passivation film 106 of an inorganic material is formed on the substrate, and a pixel electrode 107 is formed on the passivation film 106. The pixel electrode 107 includes indium tin oxide (ITO).
FIG. 2 is a cross sectional view of a color filter substrate according to the related art, wherein a color filter layer of a color filter substrate is formed by a pigment dispersion method. In FIG. 2, a photoresist film containing carbon black and titanium oxide, which have a light-shielding property, is coated on a transparent insulating substrate 201. Portions of the photoresist film are exposed to light using a mask to form a predetermined pattern. Then, the photoresist film is developed to remove the exposed portions of the photoresist film. Accordingly, remaining portions of the photoresist film are pattern after the completion of the developing process, and are hardened to form the black matrix 202.
Then, a photoresist film of azo-based red pigment is coated on the substrate upon which the black matrix 202 has been previously formed, and portions of the photoresist film are exposed to light using a mask to form a predetermined pattern. Next, the photoresist film is developed to remove the exposed portions of the photoresist film, and remaining portions of the photoresist film are hardened to form a red color filter. Using the same method as the formation of the red color filter, a green color filter and a blue color filter are sequentially formed on the substrate, thereby completely forming a color filter layer 203.
Next, a transparent conductive film, such as ITO, is deposited on an entire surface of the substrate to form a common electrode 204. The color filter substrate and the TFT substrate are bonded to each other while maintaining a predetermined gap by using spacers. The liquid crystal material is injected into the gap between the bonded substrates, thereby fabricating a liquid crystal display module.
Meanwhile, the injected liquid crystal material includes liquid crystal molecules that have a birefringence, wherein a refractive index of a long axis of the liquid crystal molecules is different from a short axis of the liquid crystal molecules. Due to this birefringence, viewing angles are changed according to a position of a viewer since a polarization state of linearly polarized light changes when the light passes through the crystal liquid material. Accordingly, when the LCD is viewed from a front side or a lateral side, the amount of light and color characteristics of the displayed image are changed depending on the position of the viewer. Thus, viewing characteristics of the liquid crystal display device are changed including brightness, contrast ratio, color shift, and gray inversion.
One proposed solution to the adverse changes of the view characteristics includes use of phase compensation technology, wherein a phase difference film is used to reduce variations in phase differences with respect to variations of the viewing positions. For example, in FIGS. 1 and 2, compensation films 108 and 205 are further formed to compensate the phase difference due to the liquid crystal material. Specifically, the compensation film 108 is arranged on the lower surface of the transparent substrate 101 of the TFT substrate, and the compensation film 205 is arranged on the lower surface of the transparent substrate 201 of the color filter substrate. Accordingly, the compensation films 108 and 205 compensate the phase variations in the liquid crystal material in opposite directions to the phase variations, wherein uniaxial or biaxial films are used as the compensation films 108 and 205.
However, foreign particles may be interposed between the compensation films 108 and 205 and the color filter and/or TFT substrates when the compensation films 108 and 205 are disposed on outer surfaces of the color filter and/or TFT substrates. Accordingly, the foreign particles complicate the fabricating process since the compensation films 108 and 205 must be removed, the foreign particles are cleaned from the substrates, and then the substrates are reattached to the outer surfaces of the substrates. Moreover, the compensation films 108 and 205 attached to the outer surfaces of the TFT substrate and the color filter substrate increase an overall thickness of the LCD device.